Welcome To The Universe

An Infinite Guide To Everything Outside Our World

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The Moon


The Earth's Moon is the only natural satellite that orbits our planet. Apart from the Earth, the Moon is the most studied object in our Solar System and it is believed that the Moon was once part of our planet.

The same side of the Moon always faces us with the other side always remaining in darkness. The dark side of the Moon was first observed by Humans when the unmanned Soviet Luna 3 mission orbited the moon and photographed it.

At its closest point, the Moon is 252,700 miles from the Earth and at its farthest, it is 338,900 miles from us.

The moon's diameter is 2,140 miles (3,476 km), 27% of the diameter of the Earth (a bit over a quarter of the Earth's diameter). The gravitational tidal influence of the Moon on the Earth is about twice as strong as the Sun's gravitational tidal influence.



The moon has no atmosphere. On the moon, the sky always appears dark, even on the bright side (because there is no atmosphere). Also, since sound waves cannot travel through a vacuum, the moon is silent; there can be no sound transmission on the moon.


The surface of the Moon is covered by countless impact craters creted by asteroids, comets, and meteorites. As there is no atmosphere, there is no protection from these objects. (most objects from space burn up in our atmosphere) These craters range in size up to many hundreds of kilometers, but the most enormous craters have been flooded by lava, and only parts of the outline are visible. The low elevation maria (seas) have fewer craters than other areas. This is because these areas formed more recently, and have had less time to be hit. The biggest intact lunar crater is Clavius which is 100 miles (160 km) in diameter.

Where did the Moon come from?

Most scientists believe that the moon was formed from the ejected material after the Earth collided with a Mars-sized object. This ejected material coalesced into the moon that went into orbit around th Earth. This catastrophic collision occurred about 60 million years after Earth itself formed (about 4.3 billion years ago). This is determined by the radioisotope dating of moon rocks.

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